In Situ Methane Determination in Petroleum at High Temperatures and High Pressures with Multivariate Optical Computing

Abstract

Multivariate optical computing (MOC) is a compressed sensing technique enabling the measurement of analytes in a complex interfering mixture under harsh conditions. In this work, we describe the design, modeling, fabrication, and validation of a sensor for the measurement of dissolved methane in petroleum crude oil at high and variable combinations of pressure (up to 82.727 MPa) and temperature (up to 121.1 °C). Both laboratory and field validation results are presented, with five separate MOC sensors yielding a RMS error of 0.0089 g/cm3 methane in high pressure/high temperature laboratory and field samples compared to 0.0086 g/cm3 methane for a room temperature laboratory Fourier transform infrared (FTIR) spectrometer using partial least-squares (PLS) regression models.

Downhole FT-MIR Spectrometer Using Perfect Metasurface Absorber

“…F OR the oil & gas industry, migration of an FT-IR spectroscopic measurement downhole would greatly expand the capabilities for in situ identification and analysis of wellbore hydrocarbons, particularly within the longer infrared wavelength regime (7 -20 µm) that has been shown useful for chemical analysis and quantification of saturate, aromatic, resin, and asphaltenic (SARA) components [1]. The miniature scale of logging systems and the geologic formation thermal environments have to date impeded efforts to transition such technologies downhole [2]. In logging while drilling (LWD) operations temperatures can exceed 175 • C with 200 MPa wellbore pressure, and sensor packages less than a 4-5 centimeters in diameter are typically necessary.…”